Light redirecting films and film systems

ABSTRACT

Light redirecting films include a pattern of individual optical elements of well defined shape on the light exit surface of the films for refracting the light entering the entrance surface of the films from a backlight toward a direction normal to the exit surface. The individual optical elements overlap and intersect each other. Also, the orientation, size and/or shape of the optical elements may be tailored to redirect more of the incident light from the backlight within a desired viewing angle.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a division of U.S. patent application No.09/909,318, filed Jul. 19, 2001, which is a continuation-in-part of U.S.patent application No. 09/256,275, filed Feb. 23, 1999, the entiredisclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

[0002] This invention relates to light redirecting films and filmsystems for redirecting light from a light source toward a directionnormal to the plane of the films.

BACKGROUND OF THE INVENTION

[0003] Light redirecting films are thin transparent or translucentoptical films or substrates that redistribute the light passing throughthe films such that the distribution of the light exiting the films isdirected more normal to the surface of the films. Heretofore, lightredirecting films were provided with prismatic grooves, lenticulargrooves, or pyramids on the light exit surface of the films whichchanged the angle of the film/air interface for light rays exiting thefilms and caused the components of the incident light distributiontraveling in a plane perpendicular to the refracting surfaces of thegrooves to be redistributed in a direction more normal to the surface ofthe films. Such light redirecting films are used, for example, withliquid crystal displays, used in laptop computers, word processors,avionic displays, cell phones, PDAs and the like to make the displaysbrighter.

[0004] The light entrance surface of the films usually has a transparentor matte finish depending on the visual appearance desired. A mattefinish produces a softer image but is not as bright due to theadditional scattering and resultant light loss caused by the matte ordiffuse surface.

[0005] Heretofore, most applications used two grooved film layersrotated relative to each other such that the grooves in the respectivefilm layers are at 90 degrees relative to each other. The reason forthis is that a grooved light redirecting film will only redistribute,towards the direction normal to the film surface, the components of theincident light distribution traveling in a plane perpendicular to therefracting surfaces of the grooves. Therefore, to redirect light towardthe normal of the film surface in two dimensions, two grooved filmlayers rotated 90 degrees with respect to each other are needed, onefilm layer to redirect light traveling in a plane perpendicular to thedirection of its grooves and the other film layer to redirect lighttraveling in a plane perpendicular to the direction of its grooves.

[0006] Attempts have been made in the past to create a single layerlight redirecting film that will redirect components of the incidentlight distribution traveling along two different axes 90 degrees to eachother. One known way of accomplishing this is to provide a single layerfilm with two sets of grooves extending perpendicular to each otherresulting in a pyramid structure which redirects light traveling in bothsuch directions. However, such a film produces a much lower brightnessthan two film layers each with a single groove configuration rotated 90degrees with respect to each other because the area that is removed fromthe first set of grooves by the second set of grooves in a single layerfilm reduces the surface area available to redirect light substantiallyby 50% in each direction of travel.

[0007] In addition, heretofore, the grooves of light redirecting filmshave been constructed so that all of the grooves meet the surface of thefilms at the same angle, mostly 45 degrees. This design assumes aconstant, diffuse angular distribution of light from the light source,such as a lambertian source, a backlighting panel using a printing oretching technology to extract light, or a backlighting panel behindheavy diffusers. A light redirecting film where all of the lightredirecting surfaces meet the film at the same angle is not optimizedfor a light source that has a nonuniform directional component to itslight emission at different areas above the source. For example, theaverage angle about which a modern high efficiency edge lit backlight,using grooves or micro-optical surfaces to extract light, changes atdifferent distances from the light source, requiring a different anglebetween the light redirecting surfaces and the plane of the film tooptimally redirect light toward the normal of the film.

[0008] There is thus a need for a light redirecting film that canproduce a softer image while eliminating the decrease in brightnessassociated with a matte or diffuse finish on the light input side of thefilm. Also, there is a need for a single layer of film which canredirect a portion of the light traveling in a plane parallel to therefracting surfaces in a grooved film, that would be brighter than asingle layer of film using prismatic or lenticular grooves. In addition,there is a need for a light redirecting film that can compensate for thedifferent angular distributions of light that may exist for a particularlight source at different positions above the source, such as backlightsused to illuminate liquid crystal displays. Also, there is a need for alight redirecting film system in which the film is matched or tuned tothe light output distribution of a backlight or other light source toreorient or redirect more of the incident light from the backlightwithin a desired viewing angle.

SUMMARY OF THE INVENTION

[0009] The present invention relates to light redirecting films andlight redirecting film systems that redistribute more of the lightemitted by a backlight or other light source toward a direction morenormal to the plane of the films, and to light redirecting films thatproduce a softer image without the brightness decrease associated withfilms that have a matte or diffuse finish on the light entrance surfaceof the films, for increased effectiveness.

[0010] The light exit surface of the films has a pattern of discreteindividual optical elements of well defined shape for refracting theincident light distribution such that the distribution of light exitingthe films is in a direction more normal to the surface of the films.These individual optical elements may be formed by depressions in orprojections on the exit surface of the films, and include one or moresloping surfaces for refracting the incident light toward a directionnormal to the exit surface. These sloping surfaces may for exampleinclude a combination of planar and curved surfaces that redirect thelight within a desired viewing angle. Also, the curvature of thesurfaces, or the ratio of the curved area to the planar area of theindividual optical elements as well as the perimeter shapes of thecurved and planar surfaces may be varied to tailor the light outputdistribution of the films, to customize the viewing angle of the displaydevice used in conjunction with the films. In addition, the curvature ofthe surfaces, or the ratio of the curved area to the planar area of theindividual optical elements may be varied to redirect more or less lightthat is traveling in a plane that would be parallel to the grooves of aprismatic or lenticular grooved film. Also the size and population ofthe individual optical elements, as well as the curvature of thesurfaces of the individual optical elements may be chosen to produce amore or less diffuse output or to randomize the input light distributionfrom the light source to produce a softer more diffuse light outputdistribution while maintaining the output distribution within aspecified angular region about the direction normal to the films.

[0011] The light entrance surface of the films may have an opticalcoating such as an antireflective coating, a reflective polarizer, aretardation coating or a polarizer. Also a matte or diffuse texture maybe provided on the light entrance surface depending on the visualappearance desired. A matte finish produces a softer image but is not asbright.

[0012] The individual optical elements on the exit surface of the filmsmay be randomized in such a way as to eliminate any interference withthe pixel spacing of a liquid crystal display. This randomization caninclude the size, shape, position, depth, orientation, angle or densityof the optical elements. This eliminates the need for diffuser layers todefeat moiré and similar effects. Also, at least some of the individualoptical elements may be arranged in groupings across the exit surface ofthe films, with at least some of the optical elements in each of thegroupings having a different size or shape characteristic thatcollectively produce an average size or shape characteristic for each ofthe groupings that varies across the films to obtain averagecharacteristic values beyond machining tolerances for any single opticalelement and to defeat moiré and interference effects with the pixelspacing of a liquid crystal display. In addition, at least some of theindividual optical elements may be oriented at different angles relativeto each other for customizing the ability of the films toreorient/redirect light along two different axes.

[0013] The angles that the light redirecting surfaces of the individualoptical elements make with the light exit surface of the films may alsobe varied across the display area of a liquid crystal display to tailorthe light redirecting function of the films to a light inputdistribution that is non-uniform across the surface of the light source.

[0014] The individual optical elements of the light redirecting filmsalso desirably overlap each other, in a staggered, interlocked and/orintersecting configuration, creating an optical structure with excellentsurface area coverage. Moreover, the individual optical elements may bearranged in groupings with some of the individual optical elementsoriented along one axis and other individual optical elements orientedalong another axis. Also, the orientation of the individual opticalelements in each grouping may vary. Further, the size, shape, positionand/or orientation of the individual optical elements of the lightredirecting films may vary to account for variations in the distributionof light emitted by a light source.

[0015] The properties and pattern of the optical elements of lightredirecting films may also be customized to optimize the lightredirecting films for different types of light sources which emitdifferent light distributions, for example, one pattern for single bulblaptops, another pattern for double bulb flat panel displays, and so on.

[0016] Further, light redirecting film systems are provided in which theorientation, size, position and/or shape of the individual opticalelements of the light redirecting films are tailored to the light outputdistribution of a backlight or other light source to reorient orredirect more of the incident light from the backlight within a desiredviewing angle. Also, the backlight may include individual opticaldeformities that collimate light along one axis and the lightredirecting films may include individual optical elements that collimatelight along another axis perpendicular to the one axis.

[0017] To the accomplishment of the foregoing and related ends, theinvention, then, comprises the features hereinafter more fully describedand particularly pointed out in the claims, the following descriptionand annexed drawings setting forth in detail certain illustrativeembodiments of the invention, these being indicative, however, of butseveral of the various ways in which the principles of the invention maybe employed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the annexed drawings:

[0019]FIG. 1 is a schematic side elevation view of one form of lightredirecting film system in accordance with the present invention;

[0020]FIG. 2 is an enlarged fragmentary side elevation view of a portionof the backlight and light redirecting film system of FIG. 1;

[0021]FIGS. 3 and 4 are schematic side elevation views of other forms oflight redirecting film systems of the present invention;

[0022] FIGS. 5-20 are schematic perspective or plan views showingdifferent patterns of individual optical elements on light redirectingfilms of the present invention;

[0023]FIGS. 5a-5 n are schematic perspective views of differentgeometric shapes that the individual optical elements on the lightredirecting films may take;

[0024]FIG. 21 is a schematic perspective view of a light redirectingfilm having optical grooves extending across the film in a curvedpattern facing a corner of the film;

[0025]FIG. 22 is a top plan view of a light redirecting film having apattern of optical grooves extending across the film facing a midpointon one edge of the film that decreases in curvature as the distance fromthe one edge increases;

[0026]FIG. 23 is an end elevation view of the light redirecting film ofFIG. 22 as seen from the left end thereof;

[0027]FIG. 24 is a side elevation view of the light redirecting film ofFIG. 22;

[0028]FIGS. 25 and 26 are enlarged schematic fragmentary plan views of asurface area of a backlight/light emitting panel assembly showingvarious forms of optical deformities formed on or in a surface of thebacklight;

[0029]FIGS. 27 and 28 are enlarged longitudinal sections through one ofthe optical deformities of FIGS. 25 and 26, respectively;

[0030]FIGS. 29 and 30 are enlarged schematic longitudinal sectionsthrough other forms of optical deformities formed on or in a surface ofa backlight;

[0031] FIGS. 31-39 are enlarged schematic perspective views of backlightsurface areas containing various patterns of individual opticaldeformities of other well defined shapes;

[0032]FIG. 40 is an enlarged schematic longitudinal section throughanother form of optical deformity formed on or in a surface of abacklight;

[0033]FIGS. 41 and 42 are enlarged schematic top plan views of backlightsurface areas containing optical deformities similar in shape to thoseshown in FIGS. 37 and 38 arranged in a plurality of straight rows alongthe length and width of the surface areas;

[0034]FIGS. 43 and 44 are enlarged schematic top plan views of backlightsurface areas containing optical deformities also similar in shape tothose shown in FIGS. 37 and 38 arranged in staggered rows along thelength of the surface areas;

[0035]FIGS. 45 and 46 are enlarged schematic top plan views of backlightsurface areas containing a random or variable pattern of different sizedoptical deformities on the surface areas;

[0036]FIG. 47 is an enlarged schematic perspective view of a backlightsurface area showing optical deformities increasing in size as thedistance of the deformities from the light input surface increases orintensity of the light increases along the length of the surface area;

[0037]FIGS. 48 and 49 are schematic perspective views showing differentangular orientations of the optical deformities along the length andwidth of a backlight surface area; and

[0038]FIGS. 50 and 51 are enlarged perspective views schematicallyshowing how exemplary light rays emitted from a focused light source arereflected or refracted by different individual optical deformities ofwell defined shapes of a backlight surface area.

DETAILED DESCRIPTION OF THE INVENTION

[0039]FIGS. 1 and 2 schematically show one form of light redirectingfilm system 1 in accordance with this invention including a lightredirecting film 2 that redistributes more of the light emitted by abacklight BL or other light source toward a direction more normal to thesurface of the film. Film 2 may be used to redistribute light within adesired viewing angle from almost any light source for lighting, forexample, a display D such as a liquid crystal display, used in laptopcomputers, word processors, avionic displays, cell phones, PDAs and thelike, to make the displays brighter. The liquid crystal display can beany type including a transmissive liquid crystal display asschematically shown in FIGS. 1 and 2, a reflective liquid crystaldisplay as schematically shown in FIG. 3 and a transflective liquidcrystal display as schematically shown in FIG. 4.

[0040] The reflective liquid crystal display D shown in FIG. 3 includesa back reflector 40 adjacent the back side for reflecting ambient lightentering the display back out the display to increase the brightness ofthe display. The light redirecting film 2 of the present invention isplaced adjacent the top of the reflective liquid crystal display toredirect ambient light (or light from a front light) into the displaytoward a direction more normal to the plane of the film for reflectionback out by the back reflector within a desired viewing angle toincrease the brightness of the display. Light redirecting film 2 may beattached to, laminated to or otherwise held in place against the top ofthe liquid crystal display.

[0041] The transflective liquid crystal display D shown in FIG. 4includes a transreflector T placed between the display and a backlightBL for reflecting ambient light entering the front of the display backout the display to increase the brightness of the display in a lightedenvironment, and for transmitting light from the backlight through thetransreflector and out the display to illuminate the display in a darkenvironment. In this embodiment the light redirecting film 2 may eitherbe placed adjacent the top of the display or adjacent the bottom of thedisplay or both as schematically shown in FIG. 4 for redirecting orredistributing ambient light and/or light from the backlight more normalto the plane of the film to make the light ray output distribution moreacceptable to travel through the display to increase the brightness ofthe display.

[0042] Light redirecting film 2 comprises a thin transparent film orsubstrate 8 having a pattern of discrete individual optical elements 5of well defined shape on the light exit surface 6 of the film forrefracting the incident light distribution such that the distribution ofthe light exiting the film is in a direction more normal to the surfaceof the film.

[0043] Each of the individual optical elements 5 has a width and lengthmany times smaller than the width and length of the film, and may beformed by depressions in or projections on the exit surface of the film.These individual optical elements 5 include at least one sloping surfacefor refracting the incident light toward the direction normal to thelight exit surface. FIG. 5 shows one pattern of individual opticalelements 5 on a film 2. These optical elements may take many differentshapes. For example, FIG. 5a shows a non-prismatic optical element 5having a total of two surfaces 10, 12, both of which are sloping. One ofthe surfaces 10 shown in FIG. 5a is planar or flat whereas the othersurface 12 is curved. Moreover, both surfaces 10, 12 intersect eachother and also intersect the surface of the film. Alternatively, bothsurfaces 10, 12 of the individual optical elements may be curved asschematically shown in FIG. 5b.

[0044] Alternatively, the optical elements 5 may each have only onesurface that is curved and sloping and intersects the film. FIG. 5cshows one such optical element 5 in the shape of a cone 13, whereas FIG.5d shows another such optical element having a semispherical or domeshape 14. Also, such optical elements may have more than one slopingsurface intersecting the film.

[0045]FIG. 5e shows an optical element 5 having a total of threesurfaces, all of which intersect the film and intersect each other. Twoof the surfaces 15 and 16 are curved, whereas the third surface 17 isplanar.

[0046]FIG. 5f shows an optical element 5 in the shape of a pyramid 18with four triangular shaped sides 19 that intersect each other andintersect the film. The sides 19 of the pyramid 18 may all be of thesame size and shape as shown in FIG. 5f, or the sides 19 of the pyramids18 may be stretched so the sides have different perimeter shapes asshown in FIG. 5g. Also, the optical elements 5 may have any number ofplanar sloping sides. FIG. 5h shows an optical element 5 with fourplanar sloping sides 20, whereas FIG. 5i shows an optical element 5 witheight planar sloping sides 20.

[0047] The individual optical elements 5 may also have more than onecurved and more than one planar sloping surface, all intersecting thefilm. FIG. 5j shows an optical element 5 having a pair of intersectingoppositely sloping planar sides 22 and oppositely rounded or curved endsor sides 23. Further, the sloping planar sides 22 and curved ends orsides 23 may have different angled slopes as shown in FIGS. 5k and 5 l.Moreover, the optical elements 5 may have at least one curved surfacethat does not intersect the film. One such optical element 5 is shown inFIG. 5m which includes a pair of oppositely sloping planar sides 22 andoppositely rounded or curved ends or sides 23 and a rounded or curvedtop 24 intersecting the oppositely sloping sides and oppositely roundedends. Further, the optical elements 5 may be curved along their lengthas shown in FIG. 5n.

[0048] Providing the individual optical elements 5 with a combination ofplanar and curved surfaces redirects or redistributes a larger viewingarea than is possible with a grooved film. Also, the curvature of thesurfaces, or the ratio of the curved area to the planar area of theindividual optical elements may be varied to tailor the light outputdistribution of the film to customize the viewing area of a displaydevice used in conjunction with the film.

[0049] The light entrance surface 7 of the film 2 may have an opticalcoating 25 (see FIG. 2) such as an antireflective coating, a reflectivepolarizer, a retardation coating or a polarizer. Also, a matte ordiffuse texture may be provided on the light entrance surface 7depending on the visual appearance desired. A matte finish produces asofter image but is not as bright. The combination of planar and curvedsurfaces of the individual optical elements 5 of the present inventionmay be configured to redirect some of the light rays impinging thereonin different directions to produce a softer image without the need foran additional diffuser or matte finish on the entrance surface of thefilm.

[0050] The individual optical elements 5 of the light redirecting film 2also desirably overlap each other in a staggered, interlocked and/orintersecting configuration, creating an optical structure with excellentsurface area coverage. FIGS. 6, 7, 13 and 15, for example, show opticalelements 5 staggered with respect to each other; FIGS. 8-10 show theoptical elements 5 intersecting each other; and FIGS. 11 and 12 show theoptical elements 5 intersecting each other.

[0051] Moreover, the slope angle, density, position, orientation, heightor depth, shape, and/or size of the optical elements 5 of the lightredirecting film 2 may be matched or tuned to the particular lightoutput distribution of a backlight BL or other light source to accountfor variations in the distribution of light emitted by the backlight inorder to redistribute more of the light emitted by the backlight withina desired viewing angle. For example, the angle that the slopingsurfaces (e.g., surfaces 10, 12) of the optical elements 5 make with thesurface of the light redirecting film 2 may be varied as the distancefrom the backlight BL from a light source 26 increases to account forthe way the backlight emits light rays R at different angles as thedistance from the light source increases as schematically shown in FIG.2. Also, the backlight BL itself may be designed to emit more of thelight rays at lower angles to increase the amount of light emitted bythe backlight and rely on the light redirecting film 2 to redistributemore of the emitted light within a desired viewing angle. In this waythe individual optical elements 5 of the light redirecting film 2 may beselected to work in conjunction with the optical deformations of thebacklight to produce an optimized output light ray angle distributionfrom the system.

[0052]FIGS. 2, 5 and 9 show different patterns of individual opticalelements 5 all of the same height or depth, whereas FIGS. 7, 8, 10, 13and 14 show different patterns of individual optical elements 5 ofdifferent shapes, sizes and height or depth.

[0053] The individual optical elements 5 may also be randomized on thefilm 2 as schematically shown in FIGS. 16 and 17 in such a way as toeliminate any interference with the pixel spacing of a liquid crystaldisplay. This eliminates the need for optical diffuser layers 30 shownin FIGS. 1 and 2 to defeat moiré and similar effects. Moreover, at leastsome of the individual optical elements 5 may be arranged in groupings32 across the film, with at least some of the optical elements 5 in eachgrouping having a different size or shape characteristic thatcollectively produce an average size or shape characteristic for each ofthe groupings that varies across the film as schematically shown inFIGS. 7, 13 and 15 to obtain characteristic values beyond machiningtolerances to defeat moiré and interference effects with the liquidcrystal display pixel spacing. For example, at least some of the opticalelements 5 in each grouping 32 may have a different depth or height thatcollectively produce an average depth or height characteristic for eachgrouping that varies across the film. Also, at least some of the opticalelements in each grouping may have a different slope angle thatcollectively produce an average slope angle for each grouping thatvaries across the film. Further, at least one sloping surface of theindividual optical elements in each grouping may have a different widthor length that collectively produce an average width or lengthcharacteristic in each grouping that varies across the film.

[0054] Where the individual optical elements 5 include a combination ofplanar and curved surfaces 10, 12, the curvature of the curved surfaces12, or the ratio of the curved area to the planar area of the individualoptical elements as well as the perimeter shapes of the curved andplanar surfaces may be varied to tailor the light output distribution ofthe film. In addition, the curvature of the curved surfaces, or theratio of the curved area to the planar area of the individual opticalelements may be varied to redirect more or less light that is travelingin a plane that would be parallel to the grooves of a prismatic orlenticular grooved film, partially or completely replacing the need fora second layer of light redirecting film. Also, at least some of theindividual optical elements may be oriented at different angles relativeto each other as schematically shown in FIGS. 13 and 16 to redistributemore of the light emitted by a light source along two different axes ina direction more normal to the surface of the film, partially orcompletely replacing the need for a second layer of light redirectingfilm. However, it will be appreciated that two layers of such lightredirecting film each having the same or different patterns ofindividual optical elements 5 thereon may be placed between a lightsource and viewing area with the layers rotated 90 degrees (or otherangles greater than 0 degrees and less than 90 degrees) with respect toeach other so that the individual optical elements on the respectivefilm layers redistribute more of the light emitted by a light sourcetraveling in different planar directions in a direction more normal tothe surface of the respective films.

[0055] Also, the light redirecting film 2 may have a pattern of opticalelements 5 that varies at different locations on the film asschematically shown in FIG. 15 to redistribute the light ray outputdistribution from different locations of a backlight or other lightsource to redistribute the light ray output distribution from thedifferent locations toward a direction normal to the film.

[0056] Further, the properties and pattern of the optical elements ofthe light redirecting film may be customized to optimize the lightredirecting film for different types of light sources which emitdifferent light distributions, for example, one pattern for single bulblaptops, another pattern for double bulb flat panel displays, and so on.

[0057]FIG. 17 shows the optical elements 5 arranged in a radial patternfrom the outside edges of the film 2 toward the center to redistributethe light ray output distribution of a backlight BL that receives lightfrom cold cathode fluorescent lamps 26 along all four side edges of thebacklight.

[0058]FIG. 18 shows the optical elements 5 arranged in a pattern ofangled groupings 32 across the film 2 that are tailored to redistributethe light ray output distribution of a backlight BL that receives lightfrom one cold cathode fluorescent lamp 26 or a plurality of lightemitting diodes 26 along one input edge of the backlight.

[0059]FIG. 19 shows the optical elements 5 arranged in a radial typepattern facing a corner of the film 2 to redistribute the light rayoutput distribution of a backlight BL that is corner lit by a lightemitting diode 26. FIG. 20 shows the optical elements 5 arranged in aradial type pattern facing a midpoint on one input edge of the film 2 toredistribute the light ray output distribution of a backlight BL that islighted at a midpoint of one input edge of the backlight by a singlelight emitting diode 26.

[0060]FIG. 21 shows a light redirecting film 2 having optical grooves 35extending across the film in a curved pattern facing a corner of thefilm to redistribute the light ray output distribution of a backlight BLthat is corner lit by a light emitting diode 26, whereas FIGS. 22-24show a light redirecting film 2 having a pattern of optical grooves 35extending across the film facing a midpoint along one edge of the filmthat decreases in curvature as the distance from the one edge increasesto redistribute the light ray output distribution of a backlight BL thatis edge lit by a light emitting diode 26 at a midpoint of one input edgeof the backlight.

[0061] Where the light redirecting film 2 has a pattern 40 of opticalelements 5 thereon that varies along the length of the film, a roll 41of the film 2 may be provided having a repeating pattern of opticalelements thereon as schematically shown in FIG. 15 to permit a selectedarea of the pattern that best suits a particular application to be diecut from the roll of film.

[0062] The backlight BL may be substantially flat, or curved, or may bea single layer or multi-layers, and may have different thicknesses andshapes as desired. Moreover, the backlight may be flexible or rigid, andbe made of a variety of compounds. Further, the backlight may be hollow,filled with liquid, air, or be solid, and may have holes or ridges.

[0063] Also, the light source 26 may be of any suitable type including,for example, an arc lamp, an incandescent bulb which may also becolored, filtered or painted, a lens end bulb, a line light, a halogenlamp, a light emitting diode (LED), a chip from an LED, a neon bulb, acold cathode fluorescent lamp, a fiber optic light pipe transmittingfrom a remote source, a laser or laser diode, or any other suitablelight source. Additionally, the light source 26 may be a multiplecolored LED, or a combination of multiple colored radiation sources inorder to provide a desired colored or white light output distribution.For example, a plurality of colored lights such as LEDs of differentcolors (e.g., red, blue, green) or a single LED with multiple colorchips may be employed to create white light or any other colored lightoutput distribution by varying the intensities of each individualcolored light.

[0064] A pattern of optical deformities may be provided on one or bothsides of the backlight BL or on one or more selected areas on one orboth sides of the backlight as desired. As used herein, the term opticaldeformities means any change in the shape or geometry of a surfaceand/or coating or surface treatment that causes a portion of the lightto be emitted from the backlight. These deformities can be produced in avariety of manners, for example, by providing a painted pattern, anetched pattern, machined pattern, a printed pattern, a hot stamppattern, or a molded pattern or the like on selected areas of thebacklight. An ink or print pattern may be applied for example by padprinting, silk printing, inkjet, heat transfer film process or the like.The deformities may also be printed on a sheet or film which is used toapply the deformities to the backlight. This sheet or film may become apermanent part of the backlight for example by attaching or otherwisepositioning the sheet or film against one or both sides of the backlightin order to produce a desired effect.

[0065] By varying the density, opaqueness or translucence, shape, depth,color, area, index of refraction or type of deformities on or in an areaor areas of the backlight, the light output of the backlight can becontrolled. The deformities may be used to control the percent of lightoutput from a light emitting area of the backlight. For example, lessand/or smaller size deformities may be placed on surface areas whereless light output is wanted. Conversely, a greater percentage of and/orlarger deformities may be placed on surface areas of the backlight wheregreater light output is desired.

[0066] Varying the percentages and/or size of deformities in differentareas of the backlight is necessary in order to provide a substantiallyuniform light output distribution. For example, the amount of lighttraveling through the backlight will ordinarily be greater in areascloser to the light source than in other areas further removed from thelight source. A pattern of deformities may be used to adjust for thelight variances within the backlight, for example, by providing a denserconcentration of deformities with increased distance from the lightsource thereby resulting in a more uniform light output distributionfrom the backlight.

[0067] The deformities may also be used to control the output ray angledistribution from the backlight to suit a particular application. Forexample, if the backlight is used to backlight a liquid crystal display,the light output will be more efficient if the deformities (or a lightredirecting film 2 is used in combination with the backlight) direct thelight rays emitted by the backlight at predetermined ray angles suchthat they will pass through the liquid crystal display with low loss.Additionally, the pattern of optical deformities may be used to adjustfor light output variances attributed to light extractions of thebacklight. The pattern of optical deformities may be printed on thebacklight surface areas utilizing a wide spectrum of paints, inks,coatings, epoxies or the like, ranging from glossy to opaque or both,and may employ half-tone separation techniques to vary the deformitycoverage. Moreover, the pattern of optical deformities may be multiplelayers or vary in index of refraction.

[0068] Print patterns of optical deformities may vary in shapes such asdots, squares, diamonds, ellipses, stars, random shapes, and the like.Also, print patterns of sixty lines per inch or finer are desirablyemployed. This makes the deformities or shapes in the print patternsnearly invisible to the human eye in a particular application, therebyeliminating the detection of gradient or banding lines that are commonto light extracting patterns utilizing larger elements. Additionally,the deformities may vary in shape and/or size along the length and/orwidth of the backlight. Also, a random placement pattern of thedeformities may be utilized throughout the length and/or width of thebacklight. The deformities may have shapes or a pattern with no specificangles to reduce moiré or other interference effects. Examples ofmethods to create these random patterns are printing a pattern of shapesusing stochastic print pattern techniques, frequency modulated half tonepatterns, or random dot half tones. Moreover, the deformities may becolored in order to effect color correction in the backlight. The colorof the deformities may also vary throughout the backlight, for example,to provide different colors for the same or different light outputareas.

[0069] In addition to or in lieu of the patterns of optical deformities,other optical deformities including prismatic or lenticular grooves orcross grooves, or depressions or raised surfaces of various shapes usingmore complex shapes in a mold pattern may be molded, etched, stamped,thermoformed, hot stamped or the like into or on one or more surfaceareas of the backlight. The prismatic or lenticular surfaces,depressions or raised surfaces will cause a portion of the light rayscontacted thereby to be emitted from the backlight. Also, the angles ofthe prisms, depressions or other surfaces may be varied to direct thelight in different directions to produce a desired light outputdistribution or effect. Moreover, the reflective or refractive surfacesmay have shapes or a pattern with no specific angles to reduce moire orother interference effects.

[0070] A back reflector 40 may be attached or positioned against oneside of the backlight BL as schematically shown in FIGS. 1 and 2 inorder to improve light output efficiency of the backlight by reflectingthe light emitted from that side back through the backlight for emissionthrough the opposite side. Additionally, a pattern of opticaldeformities 50 may be provided on one or both sides of the backlight asschematically shown in FIGS. 1 and 2 in order to change the path of thelight so that the internal critical angle is exceeded and a portion ofthe light is emitted from one or both sides of the backlight.

[0071] FIGS. 25-28 show optical deformities 50 which may either beindividual projections 51 on the respective backlight surface areas 52or individual depressions 53 in such surface areas. In either case, eachof these optical deformities 50 has a well defined shape including areflective or refractive surface 54 that intersects the respectivebacklight surface area 52 at one edge 55 and has a uniform slopethroughout its length for more precisely controlling the emission oflight by each of the deformities. Along a peripheral edge portion 56 ofeach reflective/refractive surface 54 is an end wall 57 of eachdeformity 50 that intersects the respective panel surface area 52 at agreater included angle I than the included angle I′ between thereflective/refractive surfaces 54 and the panel surface area 52 (seeFIGS. 27 and 28) to minimize the projected surface area of the end wallson the panel surface area. This allows more deformities 50 to be placedon or in the panel surface areas than would otherwise be possible if theprojected surface areas of the end walls 57 were substantially the sameas or greater than the projected surface areas of thereflective/refractive surfaces 54.

[0072] In FIGS. 25 and 26 the peripheral edge portions 56 of thereflective/refractive surfaces 54 and associated end walls 57 are curvedin the transverse direction. Also in FIGS. 27 and 28 the end walls 57 ofthe deformities 50 are shown extending substantially perpendicular tothe reflective/refractive surfaces 54 of the deformities. Alternatively,such end walls 57 may extend substantially perpendicular to the panelsurface areas 52 as schematically shown in FIGS. 29 and 30. Thisvirtually eliminates any projected surface area of the end walls 57 onthe panel surface areas 52 whereby the density of the deformities on thepanel surface areas may be even further increased.

[0073] The optical deformities may also be of other well defined shapesto obtain a desired light output distribution from a panel surface area.FIG. 31 shows individual light extracting deformities 58 on a panelsurface area 52 each including a generally planar, rectangularreflective/refractive surface 59 and associated end wall 60 of a uniformslope throughout their length and width and generally planar side walls61. Alternatively, the deformities 58′ may have rounded or curved sidewalls 62 as schematically shown in FIG. 32.

[0074]FIG. 33 shows individual light extracting deformities 63 on apanel surface area 52 each including a planar, sloping triangular shapedreflective/refractive surface 64 and associated planar, generallytriangularly shaped side walls or end walls 65. FIG. 34 shows individuallight extracting deformities 66 each including a planar slopingreflective/refractive surface 67 having angled peripheral edge portions68 and associated angled end and side walls 69 and 70.

[0075]FIG. 35 shows individual light extracting deformities 71 which aregenerally conically shaped, whereas FIG. 36 shows individual lightextracting deformities 72 each including a rounded reflective/refractivesurface 73 and rounded end walls 74 and rounded or curved side walls 75all blended together. These additional surfaces will reflect or refractother light rays impinging thereon in different directions to spreadlight across the backlight/panel member BL to provide a more uniformdistribution of light emitted from the panel member.

[0076] Regardless of the particular shape of the reflective/refractivesurfaces and end and side walls of the individual deformities, suchdeformities may also include planar surfaces intersecting thereflective/refractive surfaces and end and/or side walls in parallelspaced relation to the panel surface areas 52. FIGS. 37-39 showdeformities 76, 77 and 78 in the form of individual projections on apanel surface area having representative shapes similar to those shownin FIGS. 31, 32 and 35, respectively, except that each deformity isintersected by a planar surface 79 in parallel spaced relation to thepanel surface area 52. In like manner, FIG. 40 shows one of a multitudeof deformities 80 in the form of individual depressions 81 in a panelsurface area 52 each intersected by a planar surface 79 in parallelspaced relation to the general planar surface of the panel surface area52. Any light rays that impinge on such planar surfaces 79 at internalangles less than the critical angle for emission of light from the panelsurface area 52 will be internally reflected by the planar surfaces 79,whereas any light rays impinging on such planar surfaces 79 at internalangles greater than the critical angle will be emitted by the planarsurfaces with minimal optical discontinuities, as schematically shown inFIG. 40.

[0077] Where the deformities are projections on the panel surface area52, the reflective/refractive surfaces extend at an angle away from thepanel in a direction generally opposite to that in which the light raysfrom the light source 26 travel through the panel as schematically shownin FIGS. 27 and 29. Where the deformities are depressions in the panelsurface area, the reflective/refractive surfaces extend at an angle intothe panel in the same general direction in which the light rays from thelight source 26 travel through the panel member as schematically shownin FIGS. 28 and 30.

[0078] Regardless of whether the deformities are projections ordepressions on or in the panel surface areas 52, the slopes of the lightreflective/refractive surfaces of the deformities may be varied to causethe light rays impinging thereon to be either refracted out of the lightemitting panel or reflected back through the panel and emitted out theopposite side of the panel which may be etched to diffuse the lightemitted therefrom or covered by a light redirecting film 2 to produce adesired effect. Also, the pattern of optical deformities on the panelsurface area may be uniform or variable as desired to obtain a desiredlight output distribution from the panel surface areas. FIGS. 41 and 42show deformities 76 and 77 similar in shape to those shown in FIGS. 37and 38 arranged in a plurality of generally straight uniformly spacedapart rows along the length and width of a panel surface area 52,whereas FIGS. 43 and 44 show such deformities 76 and 77 arranged instaggered rows that overlap each other along the length of a panelsurface area.

[0079] Also, the size, including the width, length and depth or heightas well as the angular orientation and position of the opticaldeformities may vary along the length and/or width of any given panelsurface area to obtain a desired light output distribution from thepanel surface area. FIGS. 45 and 46 show a random or variable pattern ofdifferent size deformities 58 and 58′ similar in shape to those shown inFIGS. 31 and 32, respectively, arranged in staggered rows on a panelsurface area 52, whereas FIG. 47 shows deformities 77 similar in shapeto those shown in FIG. 38 increasing in size as the distance of thedeformities from the light source increases or intensity of the lightdecreases along the length and/or width of the panel surface area. Thedeformities 58 and 58′ are shown in FIGS. 45 and 46 arranged in clusters82 across the panel surface, with at least some of the deformities ineach cluster having a different size or shape characteristic thatcollectively produce an average size or shape characteristic for each ofthe clusters that varies across the panel surface. For example, at leastsome of the deformities in each of the clusters may have a differentdepth or height or different slope or orientation that collectivelyproduce an average depth or height characteristic or average slope ororientation of the sloping surface that varies across the panel surface.Likewise at least some of the deformities in each of the clusters mayhave a different width or length that collectively produce an averagewidth or length characteristic that varies across the panel surface.This allows one to obtain a desired size or shape characteristic beyondmachinery tolerances, and also defeats moire and interference effects.

[0080]FIGS. 48 and 49 schematically show different angular orientationsof optical deformities 85 of any desired shape along the length andwidth of a panel surface area 52. In FIG. 48 the deformities arearranged in straight rows 86 along the length of the panel surface areabut the deformities in each of the rows are oriented to face the lightsource 26 so that all of the deformities are substantially in line withthe light rays being emitted from the light source. In FIG. 49 thedeformities 85 are also oriented to face the light source 26 similar toFIG. 48. In addition, the rows 87 of deformities in FIG. 49 are insubstantial radial alignment with the light source 26.

[0081]FIGS. 50 and 51 schematically show how exemplary light rays 90emitted from a focused light source 26 insert molded or cast within alight transition area 91 of a light emitting panel assembly BL inaccordance with this invention are reflected during their travel throughthe light emitting panel member 92 until they impinge upon individuallight extracting deformities 50, 77 of well defined shapes on or in apanel surface area 52 causing more of the light rays to be reflected orrefracted out of one side 93 of the panel member than the other side 94.In FIG. 50 the exemplary light rays 90 are shown being reflected by thereflective/refractive surfaces 54 of the deformities 50 in the samegeneral direction out through the same side 93 of the panel member,whereas in FIG. 51 the light rays 90 are shown being scattered indifferent directions within the panel member 92 by the rounded sidewalls 62 of the deformities 77 before the light rays arereflected/refracted out of the same side 93 of the panel member. Such apattern of individual light extracting deformities of well definedshapes in accordance with the present invention can cause 60 to 70% ormore of the light received through the input edge 95 of the panel memberto be emitted from the same side of the panel member.

[0082] From the foregoing, it will be apparent that the lightredirecting films of the present invention redistribute more of thelight emitted by a backlight or other light source toward a directionmore normal to the plane of the films. Also, the light redirecting filmsand backlights of the present invention may be tailored or tuned to eachother to provide a system in which the individual optical elements ofthe light redirecting films work in conjunction with the opticaldeformities of the backlights to produce an optimized output light rayangle distribution from the system.

[0083] Although the invention has been shown and described with respectto certain embodiments, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of the specification. In particular, with regard tothe various functions performed by the above described components, theterms (including any reference to a “means”) used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed component which performs thefunction in the herein illustrated exemplary embodiments of theinvention. In addition, while a particular feature of the invention mayhave been disclosed with respect to only one embodiment, such featuremay be combined with one or more other features of other embodiments asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method of selecting a light redirecting filmfor a particular application comprising the steps of providing a lengthof film having a pattern of optical elements on or in the film thatvaries, selecting an area of the pattern that best suits a particularapplication, and removing the selected area from the film to provide thelight redirecting film.
 2. The method of claim 1 wherein the patternvaries along the length of the film.
 3. The method of claim 1 whereinthe pattern varies along the width of the film.
 4. The method of claim 1wherein the pattern varies along the length and width of the film. 5.The pattern of claim 1 wherein the length of the film comprises a rollof the film from which the selected area is removed.
 6. The method ofclaim 1 wherein the selected area is die cut from the length of thefilm.
 7. The method of claim 1 wherein the pattern is a repeatingpattern on the film.
 8. The method of claim 7 wherein the length of thefilm comprises a roll of the film from which the selected area isremoved.
 9. The method of claim 8 wherein the selected area is die cutfrom the roll of the film.
 10. A method of selecting a light redirectingfilm for a particular application comprising the steps of providing alength of film having a pattern of individual optical elements of welldefined shape on or in the film that varies, the optical elements beingquite small in relation to a width and length of the film, selecting anarea of the film that has a pattern of the optical elements that bestsuits a particular application, and removing the selected area from thefilm to provide the light redirecting film.
 11. The method of claim 10wherein the pattern is a repeating pattern.
 12. The method of claim 10wherein the pattern varies at different locations on the film.
 13. Themethod of claim 10 wherein at least some of the optical elementsoverlap, intersect or interlock each other.
 14. The method of claim 10wherein at least some of the optical elements have different shapes. 15.The method of claim 10 wherein at least some of the optical elementshave a different beam profile at different locations on the film. 16.The method of claim 10 wherein at least some of the optical elements arerandomly distributed on the film.
 17. The method of claim 10 wherein atleast some of the optical elements are oriented at different angles onthe film.
 18. The method of claim 10 wherein at least some of theoptical elements vary in at least one of the following characteristics:slope angle, density, position, orientation, height or depth, shape, andsize.
 19. The method of claim 10 wherein at least some of the opticalelements are arranged in groupings across the film, with at least someof the optical elements in at least some of the groupings having adifferent size or shape characteristic that collectively produce anaverage size or shape characteristic for each of the groupings thatvaries across the film.
 20. A method of selecting an optical panel for aparticular application comprising the steps of providing a length ofsubstrate having a pattern of optical elements on or in the substratethat varies, selecting an area of the pattern that best suits aparticular application, and removing the selected area from thesubstrate to provide the optical panel.
 21. The method of claim 20wherein the pattern varies along the length of the substrate.
 22. Themethod of claim 20 wherein the pattern varies along the width of thesubstrate.
 23. The method of claim 20 wherein the pattern varies alongthe length and width of the substrate.
 24. The pattern of claim 20wherein the length of the substrate comprises a roll of the substratefrom which the selected area is removed.
 25. The method of claim 20wherein the selected area is die cut from the length of the substrate.26. The method of claim 20 wherein the pattern is a repeating pattern onthe substrate.
 27. The method of claim 26 wherein the length of thesubstrate comprises a roll of the substrate from which the selected areais removed.
 28. The method of claim 27 wherein the selected area is diecut from the roll of the substrate.
 29. The method of claim 20 whereinthe optical panel is a backlight.
 30. A method of selecting an opticalpanel for a particular application comprising the steps of providing alength of substrate having a pattern of individual optical elements ofwell defined shape on or in the substrate that varies, the opticalelements being quite small in relation to a width and length of thesubstrate, selecting an area of the substrate that has a pattern of theoptical elements that best suits a particular application, and removingthe selected area from the substrate to provide the optical panel. 31.The method of claim 30 wherein the pattern is a repeating pattern. 32.The method of claim 30 wherein the pattern varies at different locationson the substrate.
 33. The method of claim 30 wherein at least some ofthe optical elements have different shapes.
 34. The method of claim 30wherein at least some of the optical elements have a different beamprofile at different locations on the film.
 35. The method of claim 30wherein at least some of the optical elements are randomly distributedon the film.
 36. The method of claim 30 wherein at least some of theoptical elements are oriented at different angles on the film.
 37. Themethod of claim 30 wherein at least some of the optical elements vary inat least one of the following characteristics: slope angle, density,position, orientation, height or depth, shape and size.